So the manual that comes with these mics is VERY basic. It tells you how to operate the unit, but does not elaborate what certain menu items are for. For example:

1. What is "pilot tone" and why would I ever want to turn it off?
2. What exactly is "squelch" and what is the best setting for it in the field?
3. The receiver has a menu screen that mentions software revision, can these be firmware updated and if so, how?
4. If these can output line level (as it appears they can), would it be best to connect them to the camera as line level to bypass the camera's mic preamps?
5. Has anyone else heard the theory that these Sennheiser mics (I have the omni one) sound better mounted upside down on the person? Is that to mitigate plosives? (I just got mine and haven't tried this one in the field yet).

Pilot tone is a special tone transmitted along with your microphone audio. When enabled at the receiver, the audio output remains muted until the pilot tone is received. Purpose, if you switch off your transmitter it keeps the receiver output clean of any "other" signals that may be present in the airways, useful if your receiver is always on to something like a PA system. I recommend this be left on, unless mixing G1 units with newer G2 or G3 units.

2. What exactly is "squelch" and what is the best setting for it in the field?

Squelch keeps the receiver output muted unless a signal above a certain strength is received. The higher the squelch, the stronger signal reception required to turn on the audio output. I usually leave this in the low setting. Higher settings may mute your mic signal if it falls below the squelch point.

3. The receiver has a menu screen that mentions software revision, can these be firmware updated and if so, how?

The unit firmware can be updated on most 300, 500, and 2000 series units (the EK receivers cannot be updated). You need a NET1 unit for G2, or the newer rack mount receivers with network connections for G3/2000, and the WSM software to send the update over the infrared link. The firmware updates (too date anyway) have only governed remote NET1 access and have NOT improved or changed the RF performance. If you don't use WSM or NET1 don't even worry about which firmware you have.

4. If these can output line level (as it appears they can), would it be best to connect them to the camera as line level to bypass the camera's mic preamps?

Bypassing camera mic pres could be an improvement, but this only does any good if your camera input truly has a mic pre amp bypass switch. Pro cameras usually have a line/mic/+48 type switch which actually does this. Most consumer cameras with a mic/line switch just add 50db of attenuation to accommodate line level signals, meaning you are still going through the mic preamp now with a sketchy gain structure. However, I like running line level when possible. If you are in long cable, or cable not well shielded, running line level will keep you above any noise that could be picked up in the cabling.

5. Has anyone else heard the theory that these Sennheiser mics (I have the omni one) sound better mounted upside down on the person? Is that to mitigate plosives? (I just got mine and haven't tried this one in the field yet).

I don't really buy into the upside down lav thing, but admit I have used this trick once, for the plosive problem you mentioned. Other than that I place them upright.